1. Technical Field
The present disclosure relates to a wireless communication device, a transmitter, a receiver, and a beam-forming control method.
2. Description of the Related Art
Wireless communication devices that are mainly used in microwave and millimeter-wave bands are configured having a transmitter and a receiver. Wireless communication standards for millimeter-wave bands include IEEE (Institute of Electrical and Electronics Engineers, Inc.) 802.11ad, which establishes beam-forming technology that uses a plurality of antennas and changes the directivity of signals to perform transmission and reception.
An example of the beam-forming technology specified in IEEE 802.11ad is given below (Japanese Unexamined Patent Application Publication No. 2013-179423). FIGS. 1A to 1C are drawings illustrating the configuration and operation of a wireless device described in Japanese Unexamined Patent Application Publication No. 2013-179423.
A wireless device 1 has a transmitter 1a, a first switch 1b, a first receiver 1c, a generator 1d, a second switch 1e, a second receiver 1f, and a configurator 1g. FIGS. 1B and 1C depicted below the wireless device 1 in FIG. 1A depict transmission beam patterns of the transmitter 1a. 
In the wireless device 1, the transmitter 1a wirelessly transmits a signal, and the first switch 1b switches the transmission beam pattern of the transmitter 1a that wirelessly transmits the signal. For example, the first switch 1b sets the transmission beam pattern of the transmitter 1a to transmission beam pattern a depicted in FIG. 1B. Next, the first switch 1b switches the transmission beam pattern of the transmitter 1a to transmission pattern b. Similarly, the first switch 1b switches the transmission beam pattern of the transmitter 1a in the order of transmission beam pattern c to e. In other words, the first switch 1b switches the transmission beam pattern of the transmitter 1a in such a way as to become the transmission beam patterns a, b, c, d, and e.
The first receiver 1c receives, from a reception device, a transmission beam pattern having good reception quality from among the transmission beam patterns switched by the first switch 1b. The generator 1d generates a transmission beam pattern in which the phase of the transmission beam pattern received by the first receiver 1c has been rotated. For example, the transmission beam pattern b is fed back from the reception device, and the first receiver 1c deems that the transmission beam pattern b has been received. This beam pattern b is referred to as the best sector (BS), and is defined as the sector having the best directivity from among the beam patterns a to e.
FIG. 2 is a drawing depicting an exemplary configuration of a wireless device having a transmission beam pattern switching function. A wireless device 10 has w number of antennas 12a, 12b . . . 12c and phase shifters 13a, 13b . . . 13c, and switches beam patterns by applying a phase difference with the phase shifters 13a to 13c to each branch including the antennas.
IEEE 802.11ad specifies a sequence referred to as a beam refinement protocol (BRP) for additionally carrying out fine adjustment of the patterns and additionally selecting the optimum beam pattern after the best sector has been selected. When BRP is carried out, as depicted in FIG. 1C, the generator 1d generates transmission beam patterns b1 and b2 in which the phase of the transmission beam pattern b has been rotated.
For example, the generator 1d rotates the phase of the transmission beam pattern b received by the first receiver 1c, between the transmission beam pattern b received by the first receiver 1c and the transmission beam patterns a and c adjacent to that transmission beam pattern b. Consequently, the phase of transmission beam pattern b1 lies between the transmission beam patterns b and a. Furthermore, the phase of transmission beam pattern b2 lies between the transmission beam patterns b and c.
The second switch 1e switches the transmission beam pattern of the transmitter 1a with the transmission beam pattern received by the first receiver 1c and the transmission beam pattern generated by the generator 1d. For example, according to the aforementioned example, as depicted in FIG. 1C, the second switch 1e sequentially switches the transmission beam pattern of the transmitter 1a in such a way as to become each of the transmission beam patterns b1, b, and b2.
The second receiver 1f receives, from a reception device, a transmission beam pattern having good reception quality from among the transmission beam patterns switched by the second switch 1e. For example, the transmission beam pattern b2 is fed back from the reception device, and the second receiver 1f deems that the transmission beam pattern b2 has been received. This beam pattern b2 is the best sector selected by way of BRP, this has better reception quality than the beam pattern b selected prior to BRP, and further satisfactory wireless communication can be performed.